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Prospective study to generate confidence intervals for progression after cross-linking using the ABCD Progression Display parameters in Pentacam

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First Author: E.Torres-Netto SWITZERLAND

Co Author(s):    M. Belin   M. Borgstrom   F. Gilardoni   H. Abdshahzadeh   J. Iwanczuk   F. Hafezi     

Abstract Details

Purpose:

The current ABCD progression display (Pentacam, Oculus GmbH) was designed to monitor changes in ectatic disease and determine when statistically significant change occurs. The tomographic parameters measured are the anterior and posterior radius of curvature taken from a 3.0 mm optical zone centered on the thinnest point, and minimal pachymetry. Currently, measurements are limited to keratoconic eyes prior to treatment. Measurement noise post-cross-linking was not previously determined and progression parameters after cross-linking were not established. The current study was designed to measure noise of post-cross-linking eyes and evaluate whether these measurements can serve as progression determinants after cross-linking.

Setting:

The ELZA Institute, Zurich/Dietikon (Switzerland), Ocular Cell Biology Group, University of Geneva (Geneva, Switzerland) and Center for Applied Biotechnology and Molecular Medicine at the University of Zurich (Switzerland) and University of Arizona, Tucson, Arizona (USA).

Methods:

Patients from ELZA Institute with a minimum of 9 months post-crosslinking were enrolled. Patients had a preoperative diagnosis of keratoconus, without other comorbidities. All patients discontinued contact lens wear at least one week prior to measurements. Three separate Pentacam measurements were taken, removing the patient from the Pentacam device between each measurement. A minimum of 7.5 mm of corneal coverage and an acceptable Pentacam quality score were required. At the conclusion of enrollment, U12 data files were exported for analysis. Both pooled variance estimates and one-sided confidence intervals were computed using SPSS version 23 and STATA 13 statistical software.

Results:

41 eyes of 41 patients (avg age 32.9 (range 11-63)) were enrolled with an average follow-up of 13.5 months (range 9 – 23). The average final “D” from the Belin/Ambrosio Enhanced Ectasia Display was 9.26 ± 4.37 (range 1.12 – 18.91). 80% and 95% one-sided confidence intervals for the “A” variable (anterior radius of curvature) were 0.170 and 0.261 respectively. 80% and 95% one-sided confidence intervals for “B” variable (posterior radius of curvature) were 0.136 and 0.208 and for minimal pachymetry 4.5 and 6.9 respectively. Significant differences in the range of follow-up (9-23 months) were not observed.

Conclusions:

Corneal cross-linking has had a major impact on the treatment of ectatic disease and has shown consistent results in either stabilizing or slowing the natural progression of an otherwise progressive condition. Less is known about the tomographic changes after cross-linking and what would be considered documentation of continued progression with the possibility of a retreatment. Currently, no confidence intervals are shown on the ABCD progression display once a cross-linking procedure is performed. The above parameters are planned for incorporation in the next generation of the display to allow for analysis of both the pre- and post-cross-linking cornea.

Financial Disclosure:

... receives consulting fees, retainer, or contract payments from a company producing, developing or supplying the product or procedure presented